A primary characteristic of a mobile communications system, such as a cellular telephone system, is the fact that subscribers to the system may move around. Such systems are typically realized as a network of neighboring radio cells which together provide complete coverage of the area to be serviced. Mobile radios belonging to the system are allowed to roam freely within the area of the system from one cell to another. One well-known digital mobile radio system is the Global System for Mobile communication (GSM).
In cellular radio networks like the GSM, a Home Location Register (HLR) stores location and subscriber data of mobile radios registered in the network. When a person subscribes to receive a service from a cellular network operator, the subscription is entered into the HLR of that operator. The location information of moving mobile communications units are periodically updated in the HLR. In addition to the HLR, Visiting Location Registers (VLRs) temporarily store and retrieve location and subscription information for visiting mobile subscribers. Various information (sometimes in considerable amounts) is passed between the HLR and the VLRs, e.g., subscriber's service subscriptions when mobile subscribers are roaming either in a home network or in a visited network.
When new services or new subscribers are introduced into a mobile communications system, those new services and/or subscribers must be defined in the HLR, and thereafter, the HLR must update the VLRs with the new service and/or subscriber information. Typically, new services are added to the HLR and updated in VLRs on an individual subscriber basis. If one new service is added and there are 5,000 subscribers to receive the new service, the same information must be defined and transmitted 5,000 times for each subscriber. In this kind of situation, large amounts of data must be transferred between various mobile network nodes when new services and/or subscribers are introduced. These large data transfers place a high signaling demand on the limited communication resources between the network node and also take considerable time to accomplish.
There are also situations in which large blocks of data stored in an HLR, a VLR, or other database may be lost or otherwise corrupted, e.g., as a result of a temporary power loss. In such situations, the corrupted database must be reinstated and updated from some other uncorrupted node or nodes, having accurate mobile subscriber identification, location, and service subscription information corresponding to the data which was lost or otherwise corrupted. The usual approach to restoring such information is on a subscriber-by-subscriber basis. Again, this means that the data restoration process requires considerable signaling between the corrupted and uncorrupted database nodes as well as considerable time to complete the restoration.
Related problems occur in location update procedures when a mobile unit moves to a new location area serviced by a new VLR. Typically, a location area change usually requires that some subscriber service data associated with the mobile unit be transferred to the new VLR. Depending upon the number of services subscribed to by that mobile unit, this data transfer from the HLR to the new VLR of the pertinent service information for this mobile unit may be significant. This problem is further magnified given the significant number of location update procedures performed for large numbers of roaming mobile units in metropolitan areas.
What is needed is a procedure that more readily permits new services and subscribers to be added to a mobile communications system with minimal signaling overhead. In general, data transfers between mobile communications system nodes must be performed efficiently and in a relatively short time.